Ab initio study of structural, electronic, and optical properties of perovskite materials

Abstract

I have a unique background of Physics and modeling & simulation which is ideal for research in exciting area of materials modeling and simulation. I am interested to computationally design novel materials with improved functional properties which can be used in various commercial applications. Materials modeling and simulation is an emerging area of research in Pakistan and I strongly hope that Pakistani materials industry will be able to benefit from materials modeling and simulation as it replaces the hit and trial method of materials design with a systematic approach which is inexpensive and highly accurate. The aim of my thesis is to study electronic, structural, optical and mechanical properties of Perovskite material on the basis of Density Functional Theory by using first principle or ab initio technique. Materials based on perovskite structure are commonly represented by a generic formula ABX3 where A is an alkali metal, B is an alkaline metal or transition metal or a lanthanide and X is either oxygen or a halogen group element (F, Cl, Br, I). Such materials exhibit interesting chemical and physical properties therefore have found a wide range of commercial applications such as memory devices, sensors and piezoelectric transducers. In my thesis I have selected cubic phase of NaMgF3 and up to my information no computational study and results about this material have been reported till now. I hope my study will be helpful for understanding the properties of NaMgF3 and lower mantle of earth. . The effect of hydrostatic pressure range (0 - 40) (GPa) on these properties is also studied. It is seen that NaMgF3 is indirect band gap (5.8 ev) ionic insulating material whose lattice constant decreases and indirect band gap increases with the increase of hydrostatic pressure. The study of linear optical properties predicts that optical transitions lay in ultra-violet (UV) region. Therefore, NaMgF3 can found applications in the UV region. Under high pressure, shifts in optical transition peaks are also observed. Mechanically NaMgF3 is a brittle material with B/G = 1.667. The elastic constants and elastic moduli increase with the increase of hydrostatic pressure. After this study it also concluded that the behavior of NaMgF3 is similar to the fluoro- perovskites (like KZnF3). My motivation and literature survey are given in chapter 1.After giving brief introduction about the Density Functional theory (DFT), the computational details are given in chapter 2.The results of calculations and discussions are given in chapter 3 and finally conclusions and suggestions are given in chapter 4.